Make periodic price syncs bidirectional: fetch booked + push non-booked

fetch_prices and push_prices operate on disjoint date sets so they run
concurrently via asyncio.gather in each periodic.

room_cal/workflows/prices.py

@@ -1,3 +1,4 @@
+import asyncio
 from datetime import date, timedelta
 from typing import Callable, TYPE_CHECKING
 from fastapi import APIRouter, BackgroundTasks, HTTPException
@@ -81,17 +82,23 @@ async def workflow_delete_discount(target_date: date, bg: BackgroundTasks):
   await delete_discount(target_date, schedule=lambda c: bg.add_task(_bg, c))
 
 
-async def _periodic_fetch_short(api: 'ServiceAPI') -> None:
+async def _periodic_sync_short(api: 'ServiceAPI') -> None:
   start = local_today()
-  window = get_config().global_.reservation_window_days
-  await fetch_prices(start, start + timedelta(days=window), api=api)
+  end = start + timedelta(days=get_config().global_.reservation_window_days)
+  await asyncio.gather(
+    fetch_prices(start, end, api=api),
+    push_prices(start, end, api=api),
+  )
 
 
-async def _periodic_fetch_long(api: 'ServiceAPI') -> None:
+async def _periodic_sync_long(api: 'ServiceAPI') -> None:
   start = local_today()
-  window = get_config().global_.long_window_days
-  await fetch_prices(start, start + timedelta(days=window), api=api)
+  end = start + timedelta(days=get_config().global_.long_window_days)
+  await asyncio.gather(
+    fetch_prices(start, end, api=api),
+    push_prices(start, end, api=api),
+  )
 
 
-register_periodic(_periodic_fetch_short, timedelta(hours=6))
-register_periodic(_periodic_fetch_long, timedelta(days=1))
+register_periodic(_periodic_sync_short, timedelta(hours=6))
+register_periodic(_periodic_sync_long, timedelta(days=1))